drv/core: move enable interrupts to driver init

On hubs with the USB/DFU bootloaders, interrupts are disabled by the
`cpsid` instruction in the bootloader before jumping to the main
firmware. We were reenabling them in early boot. However, this caused
the Essential hub to hang if you press and hold the button to activate
the bootloader without connecting USB then release the button after
the lights start flashing. This is fixed by moving the enable until
after all of the driver init functions have run as in the official LEGO
firmware.

Fixes: pybricks/support#821

Author: dlech

CHANGELOG.md

@@ -7,7 +7,10 @@
 ### Fixed
 - Fixed SPIKE/MINDSTORMS hubs advertising after disconnect while user program
   is still running ([support#849]).
+- Fixed Essential hub hanging on boot when bootloader entered but USB cable
+  not connected ([support#821]).
 
+[support#821]: https://github.com/pybricks/support/issues/821
 [support#849]: https://github.com/pybricks/support/issues/849
 
 ## [3.2.0c1] - 2022-12-09

lib/pbio/drv/core.c

@@ -47,6 +47,12 @@ void pbdrv_init(void) {
     pbdrv_usb_init();
     pbdrv_watchdog_init();
 
+    // Some hubs have a bootloader that disables interrupts. Has to be done
+    // here otherwise Essential hub can hang on boot if it is earlier.
+    #if PBDRV_CONFIG_INIT_ENABLE_INTERRUPTS_ARM
+    __asm volatile ("cpsie i" : : : "memory");
+    #endif
+
     while (pbdrv_init_busy()) {
         process_run();
     }

lib/pbio/platform/essential_hub/pbdrvconfig.h

@@ -111,3 +111,4 @@
 #define PBDRV_CONFIG_NUM_MOTOR_CONTROLLER   (2)
 
 #define PBDRV_CONFIG_SYS_CLOCK_RATE 96000000
+#define PBDRV_CONFIG_INIT_ENABLE_INTERRUPTS_ARM (1)

lib/pbio/platform/essential_hub/platform.c

@@ -692,9 +692,6 @@ void SystemInit(void) {
     // since the firmware starts at 0x08008000, we need to set the vector table offset
     SCB->VTOR = (uint32_t)&_fw_isr_vector_src;
 
-    // bootloader disables interrupts
-    __enable_irq();
-
     // Using external 16Mhz oscillator
     RCC_OscInitTypeDef osc_init;
     osc_init.OscillatorType = RCC_OSCILLATORTYPE_HSE;

lib/pbio/platform/prime_hub/pbdrvconfig.h

@@ -130,3 +130,4 @@
 #define PBDRV_CONFIG_NUM_MOTOR_CONTROLLER   (6)
 
 #define PBDRV_CONFIG_SYS_CLOCK_RATE 96000000
+#define PBDRV_CONFIG_INIT_ENABLE_INTERRUPTS_ARM (1)

lib/pbio/platform/prime_hub/platform.c

@@ -985,9 +985,6 @@ void SystemInit(void) {
     // since the firmware starts at 0x08008000, we need to set the vector table offset
     SCB->VTOR = (uint32_t)&_fw_isr_vector_src;
 
-    // bootloader disables interrupts
-    __enable_irq();
-
     // Using external 16Mhz oscillator
     RCC_OscInitTypeDef osc_init;
     osc_init.OscillatorType = RCC_OSCILLATORTYPE_HSE;